perjure

v.refl. (-ring) law 1 wilfully tell a lie when on oath. 2 (as perjured adj.) Guilty of or involving perjury.  perjurer n. [french from latin juro swear]

v. t. To cause to violate an oath or a vow; to cause to make oath knowingly to what is untrue; to make guilty of perjury; to forswear; to corrupt; -- often used reflexively; as, he perjured himself.